Effect of Dietary Protein on the Response of Rainbow Trout (Sa/rno gairdneri) to Aflatoxin Bl 1,2,3 D. J. Lee,
4, 5
R. O. Sinnhuber, 4, 6 J. H. Wales, 4 and G. B. Putnam 4, 7
The effect of diet on tumor incidences in populations is not well understood. Several workers have studied the influence of dietary protein on spontaneous tumor incidence and have obtained inconclusive and conflicting results. Species and strain differences complicate the problem, as do the differences in the incidence of various types of tumors (1-3). More consistent results were obtained when the influence of dietary factors on the carcinogenicity of specific compounds was studied. Newberne and Rogers (4) found that rats fed lipotropedeficient diets had a lower incidence of AFBI-induced hepatomas than did the controls. In contrast, marginally lipotrope-deficient diets increased tumor incidence. These workers also reported that AFBI produced a 4% incidence of colon cancer in rats marginally low in vitamin A, but none in adequately fed controls. The vitamin A status of the animal did not affect liver tumor incidence (5). The relationship between the physiologic effects of compounds and diet is better understood as a result of the recent increase in knowledge of drug metabolism. Dietary deficiencies of several nutrients influence drug metabolism (6-8). Kato and co-workers (9,10) reported that the level of dietary protein influenced drug metabolism and toxicity. Miranda and Webb (11) later reported that rats fed a poor quality protein (gluten) had increased hexobarbital sleeping times and lower levels of microsomal protein and cytochrome P450 in the liver than did casein-fed controls. However, the relationship between the drug-metabolizing system and carcinogenesis remains to be elucidated. While conducting long-term feeding trials at our laboratory, we observed that the type and quantity of dietary protein altered the susceptibility of rainbow trout to the carcinogenic properties of AFBI (unpublished data). This report describes the physiologic efVOL. 60, NO.2, FEBRUARY 1978
fects of AFBI in rainbow trout fed two levels of casein and FPC.
MATERIALS AND METHODS Rainbow trout (Salmo gairdneri), Mt. Shasta strain, spawned and reared at our laboratory were used. The fish weighed approximately 10 g when the experiment was initiated and had been fed either the FPC or casein control diets (diets 1 or 3) after swim up. The fish were held in 3-foot circular fiber glass tanks supplied with 3 gallons of 11.5 C water/minute. Duplicate lots of 90 fish each were fed either 0, 2, 6, 18, or 54 ppb AFBI incorporated into one of four diets (table 1). At 6, 9, and 12 months, a 30-fish sample was taken from each tank. Liver and body weights were recorded and the livers preserved in Bouin's solution for histologic examination. The AFBI was purchased from Calbiochem, Los Angeles, California, and purity checked on two-dimensional thin-layer chromatography and by the examination of the UV absorption spectrum. The toxin was dissolved in ethanol and added to the dietary oil. We prepared the diets by mixing the dry ingredients, oil, and hot (60 C) water. The thick slurry, 65% water solidified when cooled to a consistency resembling soft cheese. This was then cut into small cubes for feeding. This procedure has been used at our laboratory for over 10 years, and we have obtained good results. The FPC was obtained from the Marine Fisheries Service Southeast Utilization Research Center and we 0
0
ABBREVIATIONS USED: AFB, = aflatoxin B,; FPC = fish protein concentrate; ppb = parts per billion.
'Received March IS, 1976; revised August II, 1977; accepted August 23, 1977. 2 Supported in part by Public Health Service grant ES00541 from the National Institute of Environmental Health Sciences, National Institutes of Health. 3 Technical paper No. 4207, Oregon Agricultural Experiment Station, Oregon State University, Corvallis, Oreg. 97331. 4 Department of Food Science and Technology, Oregon State University, Corvallis, Oreg. 97331. 5 Present address: Agricultural Research Center. Washington State University, Pullman, Wash. 99163. 6 Address reprint requests to Prof. R. O. Sinnhuber. 1 We thank Mrs. L. J. Hunter for her technical assistance in preparing the histologic material and Mr. R. A. Foster, Jr., and Mr. Theodore Will for the feeding and care of the fish. We are indebted to Dr. Mary E. Ambrose of the National Marine Fisheries Service Southeast Utilization Research Service, College Park, Md., for the fish protein concentrate used in these experiments.
317
J
NATL CANCER INST
Downloaded from https://academic.oup.com/jnci/article-abstract/60/2/317/898800 by university of winnipeg user on 18 January 2019
ABSTRACT-Diets containing either 49.5% or 32% casein or fish protein concentrate (FPC) were fed to young rainbow trout (Salmo gairdneri) for 12 months. Five levels [0, 2, 6, 18, and 54 parts per billion (ppb)) of aflatoxin B, (AFB,) were given in each of four different diets. A 30·fish sample was taken at 6, 9, and 12 months to determine the influence of diet on the carcinogenicity of AFB,. Both levels of casein produced similar hepatoma inci· dences at each level of AFBI" The diet high in FPC produced more tumors than did the casein diets at 2, 6, and 18 ppb AFB" whereas fish fed the diet low in FPC had a significantly (P
4, 5
R. O. Sinnhuber, 4, 6 J. H. Wales, 4 and G. B. Putnam 4, 7
The effect of diet on tumor incidences in populations is not well understood. Several workers have studied the influence of dietary protein on spontaneous tumor incidence and have obtained inconclusive and conflicting results. Species and strain differences complicate the problem, as do the differences in the incidence of various types of tumors (1-3). More consistent results were obtained when the influence of dietary factors on the carcinogenicity of specific compounds was studied. Newberne and Rogers (4) found that rats fed lipotropedeficient diets had a lower incidence of AFBI-induced hepatomas than did the controls. In contrast, marginally lipotrope-deficient diets increased tumor incidence. These workers also reported that AFBI produced a 4% incidence of colon cancer in rats marginally low in vitamin A, but none in adequately fed controls. The vitamin A status of the animal did not affect liver tumor incidence (5). The relationship between the physiologic effects of compounds and diet is better understood as a result of the recent increase in knowledge of drug metabolism. Dietary deficiencies of several nutrients influence drug metabolism (6-8). Kato and co-workers (9,10) reported that the level of dietary protein influenced drug metabolism and toxicity. Miranda and Webb (11) later reported that rats fed a poor quality protein (gluten) had increased hexobarbital sleeping times and lower levels of microsomal protein and cytochrome P450 in the liver than did casein-fed controls. However, the relationship between the drug-metabolizing system and carcinogenesis remains to be elucidated. While conducting long-term feeding trials at our laboratory, we observed that the type and quantity of dietary protein altered the susceptibility of rainbow trout to the carcinogenic properties of AFBI (unpublished data). This report describes the physiologic efVOL. 60, NO.2, FEBRUARY 1978
fects of AFBI in rainbow trout fed two levels of casein and FPC.
MATERIALS AND METHODS Rainbow trout (Salmo gairdneri), Mt. Shasta strain, spawned and reared at our laboratory were used. The fish weighed approximately 10 g when the experiment was initiated and had been fed either the FPC or casein control diets (diets 1 or 3) after swim up. The fish were held in 3-foot circular fiber glass tanks supplied with 3 gallons of 11.5 C water/minute. Duplicate lots of 90 fish each were fed either 0, 2, 6, 18, or 54 ppb AFBI incorporated into one of four diets (table 1). At 6, 9, and 12 months, a 30-fish sample was taken from each tank. Liver and body weights were recorded and the livers preserved in Bouin's solution for histologic examination. The AFBI was purchased from Calbiochem, Los Angeles, California, and purity checked on two-dimensional thin-layer chromatography and by the examination of the UV absorption spectrum. The toxin was dissolved in ethanol and added to the dietary oil. We prepared the diets by mixing the dry ingredients, oil, and hot (60 C) water. The thick slurry, 65% water solidified when cooled to a consistency resembling soft cheese. This was then cut into small cubes for feeding. This procedure has been used at our laboratory for over 10 years, and we have obtained good results. The FPC was obtained from the Marine Fisheries Service Southeast Utilization Research Center and we 0
0
ABBREVIATIONS USED: AFB, = aflatoxin B,; FPC = fish protein concentrate; ppb = parts per billion.
'Received March IS, 1976; revised August II, 1977; accepted August 23, 1977. 2 Supported in part by Public Health Service grant ES00541 from the National Institute of Environmental Health Sciences, National Institutes of Health. 3 Technical paper No. 4207, Oregon Agricultural Experiment Station, Oregon State University, Corvallis, Oreg. 97331. 4 Department of Food Science and Technology, Oregon State University, Corvallis, Oreg. 97331. 5 Present address: Agricultural Research Center. Washington State University, Pullman, Wash. 99163. 6 Address reprint requests to Prof. R. O. Sinnhuber. 1 We thank Mrs. L. J. Hunter for her technical assistance in preparing the histologic material and Mr. R. A. Foster, Jr., and Mr. Theodore Will for the feeding and care of the fish. We are indebted to Dr. Mary E. Ambrose of the National Marine Fisheries Service Southeast Utilization Research Service, College Park, Md., for the fish protein concentrate used in these experiments.
317
J
NATL CANCER INST
Downloaded from https://academic.oup.com/jnci/article-abstract/60/2/317/898800 by university of winnipeg user on 18 January 2019
ABSTRACT-Diets containing either 49.5% or 32% casein or fish protein concentrate (FPC) were fed to young rainbow trout (Salmo gairdneri) for 12 months. Five levels [0, 2, 6, 18, and 54 parts per billion (ppb)) of aflatoxin B, (AFB,) were given in each of four different diets. A 30·fish sample was taken at 6, 9, and 12 months to determine the influence of diet on the carcinogenicity of AFB,. Both levels of casein produced similar hepatoma inci· dences at each level of AFBI" The diet high in FPC produced more tumors than did the casein diets at 2, 6, and 18 ppb AFB" whereas fish fed the diet low in FPC had a significantly (P
